This invention relates to a technique developed for coring masonry walls or the like, with less optimal, but adequate ability to core concrete and steel. In areas of the country that are susceptible to seismic shock caused by earthquakes it has become necessary to reinforce masonry buildings which, when constructed, were not built to withstand substantial seismic vibration. The method of reinforcement has generally been a technique which involves drilling long vertical holes through the masonry walls, inserting steel reinforcement bars, and grouting the bars in place with resin grout to provide the necessary reinforcement against seismic destruction. Because of the peculiar nature of drilling in an urban environment in what are often historic buildings and the final use of resin in the drill holes, there are several constraints placed upon such techniques.
The first constraint is that the holes which are to be drilled for long distances, which can be up to 100 feet in depth, must be straight so that they do not exit the side of the wall while drilling and further, that they are well-centered for structural optimization. Secondly, since the friction of the drilling process is substantial, an adequate method of cooling the bit is necessary.
The use of water for cooling the drill bit has proven to be unacceptable because the resultant leakage has a tendency to break and wash away mortar between the bricks. Also, the leakage results in an unsightly staining of the face of the masonry wall. Further, the dampness in the wall is a serious problem for the resin grouting formulation. Therefore, dry drilling is necessary not only to eliminate these problems but it is also advantageous because the resin grout can be used immediately. Wet drilling requires that the brick work first be allowed to dry so that the resin grout will cure and bond to the brick. However, dry drilling itself can create the problem of excessive dust. The excessive dust causes a problem of not only settling around the exterior as well as the interior of the building, but collects in the drill hole which plugs the hole and can cause the drill bit to bind up.
Another concern that must be dealt with in the coring of masonry walls is that present core bits which drill a cylindrical hole may leave a core in the hole which must be removed. Present methods for removing such cores have been to cut a series of holes in the face of the masonry wall to extract sections of the core. This technique obviously is undesirable because it requires each hole placed in the face of the masonry wall to be repaired. These repaired holes detract from the beauty of these buildings, many of which have historical and cultural values.
Thus, there exists an urgent need for a masonry coring technique which has the capabilities of drilling long, straight holes, utilizes a dry drilling technique which can control the extraction of the dust, keeps the drill bit cool, and provides for removing the core without having to damage the face of a masonry wall.